Variable fuel orifice carburetor



May 4,1943.

o. L. GARR ETSON VARIABLE FUEL ORIFICE CARBURETOR Filed April 21. 1942 J 32 I 25 H 24 23 1a 20 l9 1 I 9 7 5- L f I IOA 8 6 "I INVENTOR TO MANIFOLD BRANCHES v ow N L. GARRETSON Patented May 4,1943

, Phillips Petroleum Delaware mpany, a corporation of Application April 21, 1942, Serial No. 439,872

iCl. 261 -50) 1 Claim.

1 My invention relates to improvements in carburetors for internal combustion engines.

More specifically, my invention provides a posi-. tive mechanical actuation of a variable fuel oriilce by means controlled entirely by the rate of air flow into the carburetor. Thus positive proportioning of the air-fuel mixture is attained.

In my device, control of the variable fuel orifice is effected by a member disposed in the air intake pipe itself, and directly exposed and responsive to the velocity of the flowing air. The flow-responsive member is so arranged that energy imparted due to air flow tends to open the fuel valve differential across the device due to changes of main throttle opening, and this situation is a very advantageous one with respect to mixture formation at any engine speed, and particularly with respect to acceleration ability.

of the fuel flow in direct response'to the rate of air intake. r I A An object is to render the fuel flow control extremely sensitive to changes in airflow rate so as to provide for instantaneous acceleration of the engine upon movement of the main throttle toward the open position. i A further object is to provide for accurate pro-v portioning of the air and fuel charge throughout the entire speed range by a single control device.

Other objects will be recognized upon consideration of the drawing and description forming a part of this application.

Bearing in mind that conventional carburetors induce the flow of fuel through utilization of atmospheric pressure on the fuel to flow the same into a region of subatmospheric pressure, the limitations 'of such an arrangement are obvious. In contrast, my.invention takes advantage of the Superior injecting action to .be had by imposing superatmos'pheric pressure on the fuel and then subjecting this superior potential of fuel flow to control ,by throttling the fuel itself in proportion or the equivalent to impose a superatmospheric pressure on the liquid fuel.

An object of my invention is to provide for introduction of fuel under pressure to a charge forming device for ultimate consumption in a gas engine.

Another object is to provide control of the high pressurefuel flowvby means of a variable open-,

- in: orifice or valve.

It is an object to provide automatic adjustment adjustable is attached to the diaphragm and The drawing is a sectionalelevation of a de-- sirable embodiment of my invention, in which the numeral i delineates the main branch or riser of a downdraft intake manifold containing a conventional throttle valve 2. A vacuum shutoff device 3 is shown to the right of the manifold riser,

and is connected thereto by means of the line 4 below the throttle. Since this device may take many forms and is only incidental to the invention, description of this part will be limited. It is suflicient to say that the valve member 5 should seat on the nozzle Get any time when the engine is not running,and at all other times the valve member 5, because of operation of manifold suction on thediaphragm I, should be withheld .at some appreciable distance from the nozzle 6. In other words, the device is purely a shutoff, and no throttling action on the fuel nozzle is to be permitted while the engine is running.

Inside the wall supporting the nozzle 6 is an orifice I, with a secondary fuel valve 8 in cooperation therewith. These parts form the regulating device which has final control over the fuel flow, and at the same time serve as the medium by which the fuel is introduced to the air stream to form a mixture. The needle point 8 is carried by a stem 8, by means of which mo-. tion of the diaphragm I0 is transmitted to the valve. The diaphragm I0 is an element of adifferential pressure controllerfindicated generally 1 by the numeral H, and separates the'interior of the same to form compartments l2 and I3. Compartment I2.is connected to the main fuel lin H by means of a conduit l5, which latter conduit is for the purpose of pressure communication only, there being no fiow of fuel there-.

through. A tension spring lllA'which may be 'gervels to urge' the needle 8 away from the ori- A primary fuel valve composed of a seat It and i needle I1 is located before the inlet line I. which leads into chamber l3. The actuation of the needle by means outside the valve body, in the embodiment shown, is accomplished by a pair of bell cranks l9 and 20, the former of which is inside the valve body and operatively connected to the needle. The crank is outside the valve body and is mounted on a shaft 2| common to both cranks. The shaft 2| passes through the wall of the valve body and requires a packing gland (not shown) to prevent leakage of fuel to the atmosphere.

In the air inlet is mounted a plate 22, preferably of circular form, and fitted with a guide stem 23. A plurality of spoke-like members 24 are formed in the air intake, having the purpose of supporting a. guide sleeve 25 within which the stem 23 may operate freely with respect to longitudinal movement. Near the upper end of stem 23 is formed a flange member 26. A compression spring 21 has one of its ends placed against the fixed members 24, and its movable end engages the member 26 so that motion of the plate 22 is subjected to a resilient loading. Motion of the plate 22 is transmitted to the needle I! through the rocker arm 28, connecting member 29, and bell cranks l9 and 20. The rocker arm support strut 30 is pivoted at the rocker arm bearing and at the attachment lug 3|. The purpose of this orifice I6 is thereby controlled directly from the rate of air flow past the plate 22.

double-pivoted construction is to prevent bending or binding of the stem 23 upon movement by relieving the side-wise component of motion which would otherwise occur in the case of pure rotational movement of the rocker arm. The connecting link 29 may be adjusted as to length by the threaded sleeve 32, which has left and right hand threads in its respective ends.

An idling adjustment may be provided by use of a screw 33 which may be adjusted so as to hold needle l'l open sufilciently to pass the fuel required for idle running. This arrangement is only one of many possible ones, however, since the idling could be provided for by a separate idle fuel line or by other obvious and well-known means. r

The enlarged portion 34 of the air intake riser should be so proportioned that the free area be- .tween the wall of the enlarged portion and the periphery of the member 22 will be in proportion to the rate of air fiow at the resultant position of the latter member. In other words, the air fiow differential pressure at any given operating speed should be substantially constant across the plate member 22. The plate 22 is for the purpose of adjusting the fuel input to correspond with the air flow rate and not for the purpose of controlling the rate of air fiow, this function being furnished by the main throttle.

The spring 21 is one having a very low ratel By this is meant that a given increment of defiection'will result in a very slight increment in the spring load. Conversely, only a slight change in the amount of force applied to the disc 22 is required to move the plate to a new position against the spring load. Hence the differential pressure across the plate 22 will be substantially constant regardless of the rate of air flow.

In operation, the suction of the engine pistons on their intake strokes produces a reduced or subatmospheric pressure below the main throttle. Upon opening of the throttle, air enters the intake at an increased rate and thereby causing a movement of the control disc 22, which in turn acts through the mechanical linkage shown in the figure to cause a corresponding opening or the valve needle H. The flow of fuel through the value.

The differential controller I I operates to maintain a substantially constant differential pressure across the orifice [6, in a manner now to be explained. The diaphragm I0 is subjected to three principal forces, namely: (1) the fuel line pressure imposed through the conduit l5; (2) the reduced fuel pressure on the downstream side of the main fuel orifice l5; and (3) the tension load in the spring NA. The first-named force is, at all conditions of equilibrium, equal to the other two forces combined. Thus it may be seen that the be equal to the resilient force supplied by the spring. It follows that. if the spring is designed so as to have a very low rate of change in load per unit ofdeflection increment, the difference between the two pressures on opposite sides of the diaphragm, and therefore across the orifice IE will be substantially constant. Any fluctuation in either of the two pressures will result in'a slight displacement of the diaphragm and the resultant adjustment of the needle 8 with respect to the orifice 1 will re-establish the equilibrium condition.

Having a constant differential across the orifice I6, the flow therethrough becomes subject to one variable, namely, the effective free area around the needle l1. Thus, by properly shaping the needle so as to give the desired flow characteristic, accurate metering of the fuel with respect to the rate of air intake may be had. By proper matching of the fuel orifice size, the leverage ratio of the fuel valve linkage and the other factors involved, an air-fuel injection curve of any desired form may be obtained.

.It is not necessary to construct a new metering valve ll for. each mixture ratio adjustment desired, for the mixture ratio can be changed at will by adjusting the spring IOA. For example, if valve I! was constructed to give an air-fuel ratio of 15 to l for all ranges except full load and this range was 10% richer, the same percentage richening would result at full load even-though, by adjustment of spring IDA, the middle range air-fuel ratio were changed to some other figure such as 12:1 or 16:1.

From a further consideration of the operation of the differential control l3, other advantageous features of this device become apparent. For example, it will be seen that this device not only tends to keep the differential across orifice l6 constant, but also at any given fuel inlet pressure it tends to maintain a constant pressure upstream fromthe final fuel orifice 1. -If the pressure in chamber [3 tendsto rise for any reason, as.,when anzincreaseof air fiow rate causes opening of orifice 6, for example, the orifice I will be opened further by the diaphragm ID in compensation for the change of conditions. Advantage of this situation may be taken in handling the more volatile fuels by adjusting the various elements of the system so as to maintain a substantially constant high pressure throughout, at the same time maintaining the differential pressures across all but the final orifice at a low In this manner, fuels of high volatility may be utilized without troublesome vapor lock. In many cases I have found it desirable to locate throttle valve 2 at a point above fuel jet 3 so that ice would not collect on the throttle plate. This change in location does not effect the operation of the other portions of the carburetor, or even their adjustment. The upper location for the throttle also results in a greater pressure through orifice 1 and therefor better atomization.

While my improved carburetor is of particular value and high utility in the handling of high vapor pressure fuels, it is also well adapted to normal motor fuels where the, operating problems are by comparison much simpler. The scope of my invention, as well as the mode of construction or mechanical embodiment, is not tube limited except as set forth in the appended claim.

I claim:

A charge forming device for internal combustion engines having a source of fuel, under superatmospheric vapor;pressure comprising an air intake conduit, a fuel passage connecting the I air intake conduit with the source of fuel, a

drop

valve closed, said spring being under a suillcient degree of compression to maintain a substantially constant pressure differential across said valve irrespective of the rate of airflow through said air intake conduit, so that movement ofthe pressure responsive valve produces a corresponding movement of the primary fuel valvelproportional to the rate of air-flow through said air intake conduit, a pressure responsive diaphragm operably connected with the secondary fuel valve communicating on one side with the fuel passage upstream of the primary fuel valve and on the opposite side with'the fuel passage downstream of said primary fuel valve and spring means opposing the pressure exerted on said last diaphragm by fuel upstream of the primary fuel valve, to. maintain a substantially constant pressure differential across said primary fuel valve, 'so that movement of said pressure responsive valve in response to air-flow 7 produces a'proportional flow of fuel through said passage by actuation of theprimary fuel valve.

OWEN L. GARRETSON. 

